As used herein, the terms .alpha. and .beta. when used to identify carbon nitride crystalline phases shall refer to the crystalline structures of .alpha. and .beta. respectively, of silicon nitride (.alpha.-Si.sub.3 N.sub.4 and .beta.-Si.sub.3 N.sub.4), both of which have known crystal structures. Since .alpha. and .beta. carbon nitride, hereinafter sometimes referred to as .alpha.-C.sub.3 N.sub.4 and .beta.-C.sub.3 N.sub.4 have not heretofore been made, the .alpha. and .beta. terms would otherwise have no meaning unless referred to known crystal structures. High bulk moduli were predicted for covalently bonded carbon-nitrogen materials on a theoretical basis by Cohen, M. L., Phys. Rev. B32, 7988 (1985). However, heretofore, it is not believed that anyone has successfully made any .beta.-carbon nitride phase nor any .alpha.-carbon nitride phase. Silicon nitride itself is of considerable interest for use in high performance engineering materials because of its strength and hardness, high decomposition temperature and excellent resistance to corrosion and wear. For example, silicon nitride may be used as a high temperature structural material in engine components and cutting tools. Since it has a low mass density, and it may be made into light weight, low inertia components which have excellent strength-to-weight ratios. For those same reasons, carbon nitride, which theoretically was predicted to have a large bulk modules by Liu, A. Y. and Cohen, M. L. Science 245, 841 (1989); carbon nitride is even more desirable for such uses.
It is therefore an object of the present invention to provide two new crystalline carbon nitride compounds, hereafter referred to as .alpha.-carbon nitride and .beta.-carbon nitride, wherein the .alpha. and .beta. refer to the known .alpha. and .beta. crystalline structures of silicon nitride.
It is further an object of the present invention to provide methods for preparing such .alpha. and .beta. carbon nitrides.
These and other objects will be apparent from the following description from the appended claims.